HOPE geomembrane was exposed to leachate generated from an existing hazardous waste landfill for up to one year both in the laboratory (EPA Method 9090) and in a leachate collection sump at the site. Various mechanical, physical, and microstructural properties were monitored after 30, 60, 90, 120, and 365 days of exposure in the laboratory and after 120 and 365 days in the sump. Comparison of the tensile property results among the laboratory and sump-exposed samples showed considerable similarity. Variability in the geomembranes tested was evident. Test results are presented, along with a discussion on measuring the apparent variability of the geomembrane.